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Abstract:
The effects of amantadine on early cognitive processes were
investigated in 24 patients with multiple sclerosis and fatigue
using objective electrophysiological measures, i.e. Event Related
Potentials (ERP). Two different ERP measures (selection negativity
SN and lateralized readiness potentials LRP) were applied to assess
two major cognitive processes: stimulus selection and response
selection. Additionally reaction times RT were measured. The
patients underwent neuropsychological testing and the lesion load
was measured on MRI images prior to the electrophysiological
measurement. The 24 patients were engaged in double-blind, placebo
controlled, cross-over within subjects design study. After
randomization into a verum and a placebo group the patients
performed twice a stimulus choice/response choice task. Results:
Patients with a longer history of MS (> 7 years) had different
RT, SN and LRP patterns when compared to MS patients with a
relatively short disease duration (< 7 years). Moreover, the
former group of patients showed significant effects (improvements),
when treated with amantadine, on RTs, SN and LRP amplitudes than
patients in the latter group (< 7 years). A significant
correlation was found between the RT`s and the total lesion volume
(TLV) measured on the MRI. As expected a significant difference was
found between the TLV of the patients with a long MS duration and
those with a short one. No amantadine effects were found with
regard to fatigue. Conclusion: Amantadine improves cognitive
processing only in patients with a long MS duration. Neural tissue
loss becomes more important with the increasing disease duration.
Other studies have already shown that damage or partial loss of
neural tissue is compensated by a higher activity of the remaining
neural structures. Amantadine may enhance this process by
increasing the information processing capabilities of the remaining
neural tissue.
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